stream data from m code to simulink block

i have do stream the data from my m code into simulink block using 'set_param' such that suggest in the past http://www.mathworks.com/matlabcentral/newsreader/view_thread/324671.... my constants block was change the value while the m code is continuously run but the value at display block in value was show as in the constant block..below is my code

ax=int2str(ax);
  ay=int2str(ay);
  az=int2str(az);
  gx=int2str(gx);

    set_param('model1/Constant','Value',ax);
    set_param('model1/Constant1','Value',ay);
    set_param('model1/Constant2','Value',az);
    set_param('model1/Constant3','Value',gx);

the value at display will show after i stop the m code...any one can help me..please